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Full-Text Articles in Polymer Science
Elastic Breakup In Uniaxial Extension Of Entangled Polymer Melts, Yangyang Wang, Pouyan Boukany, Shi-Qing Wang, Xiaorong Wang
Elastic Breakup In Uniaxial Extension Of Entangled Polymer Melts, Yangyang Wang, Pouyan Boukany, Shi-Qing Wang, Xiaorong Wang
College of Polymer Science and Polymer Engineering
Five entangled melts, with the number of entanglements per chain ranging from 25 to 160, have been studied to illustrate how cohesive strength can be overcome in either continuous or interrupted extension (i.e., during or after uniaxial stretching). The internal elastic stress due to chain deformation from imposed strain appears to be the cause of the observed yielding behavior that reveals scaling laws. The visual signature of the elastic breakup is the occurrence of nonuniform extension. The yield phenomena may be understood at a force level.
New Theoretical Considerations In Polymer Rheology: Elastic Breakdown Of Chain Entanglement Network, Shi-Qing Wang, Sham Ravindranath, Yangyang Wang, Pouyan Boukany
New Theoretical Considerations In Polymer Rheology: Elastic Breakdown Of Chain Entanglement Network, Shi-Qing Wang, Sham Ravindranath, Yangyang Wang, Pouyan Boukany
College of Polymer Science and Polymer Engineering
Recent experimental evidence has motivated us to present a set of new theoretical considerations and to provide a rationale for interpreting the intriguing flow phenomena observed in entangled polymer solutions and melts [P. Tapadia and S. Q. Wang, Phys. Rev. Lett. 96, 016001 (2006); 96, 196001 (2006); S. Q. Wang , ibid. 97, 187801 (2006)]. Three forces have been recognized to play important roles in controlling the response of a strained entanglement network. During flow, an intermolecular locking force f(iml) arises and causes conformational deformation in each load-bearing strand between entanglements. The chain deformation builds up a retractive force f(retract) …
Photopolymerization-Induced Directional Crystal Growth In Reactive Mixtures, Soo Jeoung Park, Pankaj Rathi, Thein Kyu
Photopolymerization-Induced Directional Crystal Growth In Reactive Mixtures, Soo Jeoung Park, Pankaj Rathi, Thein Kyu
College of Polymer Science and Polymer Engineering
Photopolymerization-induced crystallization has been demonstrated in blends of polyethylene oxide-diacrylate at temperatures above the depressed melting temperature of the crystalline component. Upon exposure to ultraviolet irradiation, the melting transition curve moves upward and eventually surpasses the reaction temperature, thereby inducing phase separation as well as crystallization. The present paper demonstrates the occurrence of directionally solidified interface morphologies of polymer crystals subjected to a photointensity gradient. The epitaxially grown seaweed or degenerate structures were observed at the circumference (low-intensity region) while the dense branched spherulites developed at the core high-intensity region.
Discrepancy In Determination Of Chi Parameters By Melting Point Depression Versus Small-Angle Neutron Scattering In Blends Of Deuterated Polycarbonate And Isotactic Poly(Methyl Methacrylate), Thein Kyu, Rushikesh A. Matkar, Dong Soo Lim, Chechian Ko
Discrepancy In Determination Of Chi Parameters By Melting Point Depression Versus Small-Angle Neutron Scattering In Blends Of Deuterated Polycarbonate And Isotactic Poly(Methyl Methacrylate), Thein Kyu, Rushikesh A. Matkar, Dong Soo Lim, Chechian Ko
College of Polymer Science and Polymer Engineering
The discrepancy in the chi interaction parameters of deuterated polycarbonate/isotactic poly(methyl methacrylate) blends as determined by the melting point depression approach and the small-angle scattering technique is reported. We have modified the Flory diluent theory by removing the inherent assumption of complete rejection of the solvent from the crystal solid by taking into consideration the crystal-amorphous, amorphous-crystal, and crystal-crystal interactions. The discrepancy in chi values obtained by the two methods is discussed.
A Correlation Between Velocity Profile And Molecular Weight Distribution In Sheared Entangled Polymer Solutions, Pouyan E. Boukany, Shi-Qing Wang
A Correlation Between Velocity Profile And Molecular Weight Distribution In Sheared Entangled Polymer Solutions, Pouyan E. Boukany, Shi-Qing Wang
College of Polymer Science and Polymer Engineering
In this work we attempt to answer several questions concerning the flow characteristics of entangled polymer solutions in a sliding plate shearing cell. We explore (a) how the molecular weight distribution affects the velocity profile in simple shear, (b) whether the observed shear banding is consistent with a nonmonotonic constitutive model, (c) whether the flow response and velocity profiles are different in simple shear depending on the different modes of shear. Our results provide a comparison with recent reports on a polydisperse polymer sample [Tapadia and Wang, Phys. Rev. Lett. 96, 016001 (2006); Tapadia, et al., Phys. Rev. Lett. 96, …
How Does The Coupling Of Secondary And Tertiary Interactions Control The Folding Of Helical Macromolecules?, Vikas Varshney, Gustavo A. Carri
How Does The Coupling Of Secondary And Tertiary Interactions Control The Folding Of Helical Macromolecules?, Vikas Varshney, Gustavo A. Carri
College of Polymer Science and Polymer Engineering
The authors study how the simultaneous presence of short-range secondary and long-range tertiary interactions controls the folding and collapse behavior of a helical macromolecule. The secondary interactions stabilize the helical conformation of the chain, while the tertiary interactions govern its overall three-dimensional shape. The authors have carried out Monte Carlo simulations to study the effect of chain length on the folding and collapse behavior of the chain. They have calculated state diagrams for four chain lengths and found that the physics is very rich with a plethora of stable conformational states. In addition to the helix-coil and coil-globule transitions, their …